The present invention relates to the electronic networking industry. This includes any device or system containing devices which communicate with each other via a bus connection. This bus connection could include wireless or wire connected bus systems and devices.
These network systems allow the communication among several interacting devices such as control components, mobile devices such as tablets and i-phones, industrial distributed modules including I/O modules and terminals.
Particularly, this discussion pertains to automatically addressing several modules for use in a network. In one embodiment of the invention several devices are connected to a controller thru a bus connection. The controller assigns specific addresses to modules so that the devices and the controller can communicate with each other.
The prior art cited in patent Ser. No. 08/060,658 (McFarland) discusses a daisy chain configured network. In this arrangement each device is in communication with the adjacent devices. At power up each device awaits a signal containing a series of pulses on its respective input bus connection. When this signal is received it outputs, to the adjacent device, a signal with an additional pulse. The last device in the network sends its signal back to a controller which is also connected on the daisy chained bus. The controller then assigns addresses to each device sequentially given the number of devices on the network.
This scheme of automated addressing though simple has several shortcomings. First if a device is not receptive to this addressing scheme it will not allow automated addressing of all devices on the network. Second there is no means of accounting for a device which has a hardwired address. For instance a device could not be given an address manually by setting latching switches. Third cycling power at the devices and the controller is required to initiate the addressing cycle. Depending on the type of controller, devices and most importantly the application, cycling power could damage a device or cause safety concerns.
Other prior art is cited which includes patent 07755505 (Johnson). Power up is also required to initiate this scheme. The controller issues a “Clear Found Flag” to all devices using each address, next it polls each address for an acknowledgement. If an address is received it stores the address and a random number that is generated by the responding device. Next the controller requests the serial number from the device. If a serial number has been received the serial number is saved at the controller. The controller sends a “Set Found Flag” message to the device. The controller conducts several tests during this process which can cause the process to repeat. This is because there is no means of sequencing the device acknowledgements, so corrupt acknowledgements are a frequent reason for repeating the process. Also the number of devices on the network is required, during the assignment process if the number of devices have not received a “Set Found Flag” signal the process is repeated. This results in unpredictable addressing duration. Once all the serial numbers have been found the addresses are assigned sequentially to each device given the serial number.
Patent 5952934 (Matsumoto) discloses a scheme wherein a controller (center unit) sends a terminal assignment request message on a control address (channel) which causes devices to respond with an acknowledgement and a temporary device ID. This temporary ID is then used to communicate with the controller and so the controller can assign a specific address. As part of this scheme if the device acknowledgement (including the temporary device ID) is invalid the process is repeated. This patent also teaches the use of a timer at the controller. This timer is randomly set and is used to restrict the controller from receiving responses from devices when a set of specific combinations of device and controller acknowledgements are not consistent with a successful assignment. In this case the controller will not receive a signal until the timer has expired. As with the previous patented devices an unpredictable addressing duration results.
An advantage of the applicant's approach for automatic addressing is that a fixed amount of time is needed. As can be understood by the above prior art, a controller could get stuck looking for devices for a long period of time. This problem is eliminated by fixing the number of available addresses, the amount of time allowed for any device to respond back to the controller and understanding that no devices are left to be addressed.
An additional advantage is that devices that do not understand the approach are excluded from participating. This is because the network is originally tested for each of a list of available addresses. A response to an address eliminates the address from the available addresses for use in the approach.
During this testing of available addresses, mentioned above, any devices which have fixed or mechanical switches setting their respective addresses are also excluded from participating. This eliminates confusion over how the address has been established. For example maintenance personnel can remove and replace legacy and fixed address devices without being concerned that the addresses will contend after an automated assignment.